Purpose: To study the diameter response of retinal arterioles as a function of the arteriolar diameter.
Methods: Ten healthy young volunteers aged 22 to 33 years were subjected to diameter measurement of four successive segments of a retinal arteriole with a retinal vessel analyzer (RVA). At each of the segments, the diameter response during an increase in the systemic blood pressure (mean arterial pressure [MAP]) induced by isometric exercise was compared to the diameter of the arterioles during rest.
Results: The isometric exercise induced a significant contraction of the studied vessel segments averaging 2.5% +/- 0.4% (P < 0.0001, n = 40). There was a significant negative correlation between the baseline diameter of the studied vessel segments and the diameter response induced by isometric exercise (P = 0.02).
Conclusions: The blood pressure-induced diameter response of retinal arterioles increased with decreasing diameter of the vessels. The results indicate that the distal retinal arterioles play a major role in the regulation of retinal blood flow.